We will determine if neonatal thymectomy will influence the course of future enterococcal pyelonephritis. We will attempt to transfer pyelonephritis by parabiotic attachment of rats with bacteriologically "burned out" Escherichia coli pyelonephritis to syngeneic normal recipients. We will examine the histologic course of E. coli pyelonephritis after viable bacteria are no longer present in the kidney. We will compare the production of iron binding catechols among strains of E. coli of differing virulence by chemical means in order to determine whether there is a relation to virulence. We intend to develop single stranded DNA probes for use in DNA-DNA and DNA-RNA hybridization experiments to determine the presence of non-culturable E. coli in rat kidneys and urine. A single stranded probe has the advantage over double stranded nucleic acid probes of not self annealing. Because of this latter quality, single stranded probes can be used to drive a reaction to completion permitting detection of minute quantities of nucleic acid in extremely short periods of incubation.